This invention relates to printers and, more particularly, to a core that has a web material wound around it and a shaft for supporting web materials that will rotate when web materials designed to use with the machine are used, but will not rotate if web materials not designed for use by the machine are used, or if the web material is loaded in a position in which the web of material will not work properly in the machinery.
It is well-known to wind a web around the outer surface of a core and then mount the core onto a shaft for performing numerous operations, such as label printing. Typically, i.e., ink ribbons, labels, thermal transfer ribbons, etc. on continuous web substrate or the like are mounted onto the cores. The shafts will rotate in a direction to either remove or add web onto the core. An example of the foregoing is in a label printer wherein the inked ribbon is wound on a core and then is mounted onto a first shaft, past a printing station and connected to a driven take-up roller on a second shaft. Another example is a series of labels that are carried by a continuous web of a release liner which are successfully advanced over a platen which is wound around the outer surface of a core. The core containing the continuous web is mounted onto a shaft past a printing station and the continuous web is then connected to a take up roller on a second shaft.
There have been various prior art cores that are adapted to be removeably received on shafts. For instance, U.S. Pat. No. 5,947,618 issued to Keller et al. (hereinafter referred to as xe2x80x9cKeller-1xe2x80x9d) discloses an improved core designed to be frictionally engaged onto the spindle to releasably hold the core in position on the spindle. The core has three abutment faces on the interior surface and one of the abutment faces is cooperable with an abutment on the shaft to hold the core in proper position. However, in Keller-1, the core and spindle disclosed do not prevent the shaft from rotating if the incorrect web material is used. When the incorrect web material is used, the shaft does not stop rotating, thereby preventing the machine from functioning properly.
Another core and shaft assembly is disclosed in U.S. Pat. No. 5,833,377 issued to Keller et al. (hereinafter referred to as xe2x80x9cKeller-2xe2x80x9d) in which an improved core and an improved shaft are disclosed which are frictionally engaged by means of a spring finger. The core has an abutment face for limiting movement of the core onto the shaft as well as a ramp to releasably hold the core in position on the shaft. The Keller-2 patent discloses the interrelationship of the core and the shaft, but does not anticipate that the shaft will be inoperable with a core with web material mounted incorrectly in the machine. Again, there is no cessation of machine operation if a core with ink ribbon wound around it is mounted in the incorrect direction, or if a core with an incompatible ribbon wound there around for printing with that printer is mounted onto a shaft.
When a core with web material not designed for use with a particular machine is placed on. a shaft, significant disadvantages to the user may be evident which have not been solved by the prior art, such as excessive wear on the print head leading to premature failure of the print head, ribbon breakage due to incompatibility of the installed web material with the print head, and contamination of the web material leading to poor print quality. In the case of a thermal printer, cores of web material that comprise material that will not work properly in the machine can cause excessive wear of the print head. In thermal printing, the print head contacts the backcoating of the thermal transfer ribbon. Heat is transferred through the backcoating to melt the ink adhered to the opposite side of the ribbon. This causes the ink to be transferred onto the substrate in contact with the ribbon. A thermal printer ribbon has a back coating comprising a material that typically has a low coefficient of friction. Premature failure of the print head occurs when the back coating does not have a coefficient of friction that is compatible with the thermal print head, and when the backcoating repeatedly contacts the print head in the course of the thermal printing process. Also, the web material could break due to incompatibility of the ribbon with the temperature of the print head. If the print head is too hot for the ink ribbon that was incorrectly used, the web of ink ribbon would break when in contact with the heat of the thermal print head. Breakage of the ribbon due to incompatibility of the ribbon with the temperature of the print head leads to machine inoperability. In addition, when an inferior quality ink ribbon is used, a problem, such as contamination of the ribbon related to the varied manufacturing processes, could lead to premature wear of the print head and ultimate machine failure. Particles from contamination can be deposited on the print head. When the print head contacts a ribbon with foreign particles on the ribbon, the print head will be scratched when it contacts the ribbon. When the print head is scratched, inferior print quality as well as premature print head failure will occur. In the case of print quality, this could be substantial loss of revenue. There are specific printer applications, such as postal printing applications, which require higher levels of print quality and would result in loss of revenue when characters are not readable, i.e., a poorly printed postal indicia may have no value.
In the case of a label printer, a series of labels is carried by a web and is Is successfully advanced over a platen where each label is printed by a print head. After each label is printed, the carrier web is advanced around a delaminator where the printed label is peeled from the carrier web for application to an article. The web material with labels is wound around the core. When a core of web material with label stock having a greater or lesser thickness than the machine requires is used, jams occur in the continuous web feed path. Also, tension on the machine parts is experienced which contributes to machine failure. When cores of continuous webs of labels not specifically designed for use in the particular printer are placed on the shafts of the label printers for the label printing operation, the label stock can jam in the continuous web feed path. Machine jams can result from any of the following: premature release of labels from the carrier web, labels too thick to proceed along the tenuous paper path, or similar paper path failures.
A disadvantage of the prior art is that incorrect cores of web material can be placed on the shaft of the machine, and the machine will continue operating.
This invention overcomes the problems of the prior art by providing a core and shaft assembly that enables a user to place a core of web material onto the shaft in a position for feeding the web material. To accomplish the foregoing, this invention provides a web material core with axially positioned areas that mate with a shaft that has upwardly protruding pins thereby preventing the shaft from rotating when a core with web material wound around it that will not work in the machine is placed on the shaft.
In accordance with one embodiment of the invention is the combination of a core and a shaft. The core is generally tubular in shape onto which a web of material can be wound or supported and has at least one axially extending slot. The slot extends from the end of the core and ends in the central portion of the core. Also, the slot in the core is cut from the inner surface to the outer surface. The shaft subassembly comprises an inner shaft having notches and an outer shaft having spring-loaded pins. The spring1 loaded pins mate with the notches on the inner shaft when a core, which is not designed for use by the given machine, is mounted onto the shaft. In that case, the web material will no longer be advanced because the pins prevent the shaft from rotating. A core that has web material wound around it that is not compatible with the machine will not have slots positioned to mate with the pins present in the outer shaft on the machine. As the core with web material wound around it that is not compatible with the machine is placed onto the shaft, the pins located in the outer shaft on the machine will be forced downward into the notches, positioned below the pins on the inner shaft. When the pins are forced downward into the notches on the inner shaft, the shaft will only rotate to the point at which the notch end is reached. At this point, the shaft assembly will cease rotating, thereby causing the core with the web material wound around it to stop rotating.
The spring-loaded pins located in the outer shaft have two planar sides with a curved topside allowing a core to be slideingly mounted onto the shaft whilethe planar sides position the core on the shaft and prevent the core from rotating. A spring retainer portion on the pin positions the pin within the outer shaft.
An alternative embodiment is to provide a core with web material wound around it that has axially extending grooves whereby the grooves extend an unequal distance from each end of the core toward the central portion. There is an indent at the central portion position at the end of the groove, allowing the spring-loaded pins located on the outer shaft to engage. When the core is slideably mounted onto the shaft, the spring-loaded pins are forced upward into the groove of the core andwill ultimately lock the core into the operating position when the spring-loaded pins reach the indent at the end of the groove on the core.